Efficacy of indigenous plant growth-promoting rhizobacteria and Trichoderma strains in eliciting resistance against bacterial wilt in a tomato

Bacterial wilt of tomato caused byRalstonia solanacearumis a serious threat to tomato production worldwide. For eco-friendly management of bacterial wilt of tomato, the rhizospheric microorganisms belonging to the generaBacillus(6 isolates),Brevibacillus(1 isolate),Pseudomonas(3 isolates), andTrichoderma(8 isolates) were studied for their ability to induce innate immunity in tomato, individually and in combination againstR. solanacearumin greenhouse and field studies. In laboratory studies, maximum germination percent of 93%, vigor index of 1609 was noted in seed bacterization withP. fluorescensPf3, followed by 91% germination, vigor index of 1593 in treatment withT. asperellumT8 over control. Under greenhouse conditions, protection against bacterial wilt in individual treatments with PGPRs ranged from 38 to 43% andTrichodermasp. ranged from 39 to 43% in comparison to control. In comparison to individual seed treatment, among different combinations, maximum seed germination percent of 97% was recorded with combinationP. fluorescensPf3 +T. longibrachiatumUNS11. In greenhouse studies' combination seed treatment withP. fluorescensPf3+ T. longibrachiatumUNS11 offered an impressive 62% protection against bacterial wilt over control. Similarly, under field conditions, seed treatment withP. fluorescensPf3+ T. longibrachiatumUNS11 resulted in 61% protection. The innate immunity triggered by eco-friendly seed treatment was analyzed by expression to defense-related enzymes such as peroxidase, phenylalanine ammonialyase, and polyphenol oxidase in comparison to control. This study indicated that the potential benefits of using combination treatments of beneficial microorganisms in effectively inducing resistance are possible for dual benefits of enhanced plant growth, tomato yield, and pathogen suppression